Polymerization of olefines



Patented Nov. 1,;

o u OLYMERIZATIONDF'CLEFINES I f Donald'RQStevens, Swissvale, :and william Ae 1 Gruse, Willrinsburg, Pa assignors to Gulf .Research & Development Company, Pittsburgh Pa a corporation of Delaware No Drawing.

Application November' 17-, 1936, Serial No. I a

ciai sjlol. 2605-683) phase removing the gases and vapors and subsequently recovering the normally liquid polymers therefrom; allas more iully'hereinafter set forth andasclaimed. R

In our copendi applicationserial No, 54,336,

5 filed December 13, 193 5,wedisclosed a process of poLvmerizing iso butylenecomprisingabsorption of iso-butylene in 60 .to 65 percent sulfuricacid at atmospheric temperatures or thereabouts-,the acid-olefine mixture being-subsequently adjusted in acidity to between 45 and-55 grams per: 100 cc. (or the absorption being stopped when the acidity reaches this value) andethe acid-olefine mixture being then warmed to' separate the polymers. This twostep process is a modification or the well known 'Butlerowfmethod described in the,

literature as far back as 1877. V, Our present invention comprisesa process of polymerizing gaseous oleiines in which theab- ,sorption and polymerizationof olefine in the acid is carried out in a singlestep, According to our present: invention, the oleflne gas consisting of or containing isobutylene is V brought'intointimate contact with sulfuric acid of moderate strength, not exceeding about 65 per cent, at an elevated temperature, said temperature being at least as high as thedewpoint of the composite polymers 1 in the eflluent gases,

whereby condensation ..or ?retention .of polymers in the acid mixture is prevented. The polymers are removed .as fast as they. are formed, in vapor 1 form, V the eflluent gases being subsequently treated by cooling or absorption to condense and recover the polymers. Preferably, however, the" contact between the olefinegas and theiacid is carriedout at a temperature substantially above the dew point of the totalpolymer, the preierred operating temperatures being. from about 100 to I about 200 c. c

Asindicated nereinabpv, thfstr gtnibrth 0 acid should not be in excess of about,65 per cent,

and the best strength is62 to 63 percent, but due to the operating temperatures some concentration of the acid normally occurs in a continuous operation. Consequently, when the process is carried out in continuous manner'we prefer to introduceacidof lower strength, for example from i to per-cent sulfuric acid and to remove the acid from contact with the gases at a point correspondingto'a strength oi from 60 to per cent. I

Wehave round it advantageous to introduce 3 theole'fine gas 'and'sulfuric acid of from50 to 60 per-cent'into suitable contact apparatuscompris-- -ing a zone of extended surface, for example a tower filled with pumice, tile, broken stone. or the like, "the gas'andacid traveling concurrently lo through the zone in contactwithj each othezfland separationof the gas-from the ac id taking place at a point corresponding to an acid strength of from 60 to 65' per cent. Theacid may then be di- 'luted with water to the initial strength and re 15 cycled to the polymerizing zone,whilethe' gases and vapors are't'reated for the recovery of the polymers contained therein, a's'for example by condensation or'absorption. i j

7 Alternatively, sufiicientmoisturejmfly b dded 20 to the olefine gasbefore being brought lntocontact with the acid in order to offset the normal dehydrating effect and to maintain the acid at the desired concentration; in thisinstance the acid may be introduced in the desired strength of 5 60 to 65 per cent, the amount of moisture in the gas being regulated to hold the acid at this concentration. Where this is done, countercurrent flow of gas and acid, or simply passage or the gas through a zone containing a batch of the acid, 0,

may be employed with good results.

While pure iso-butylene may b'eemployed as the starting material, it will ordinarily be advantageous to employ the so-called butane cut obtained from refinery gasespas'for-example in the 35 debutanization of cracked gasoline. 1 'Such' a cut will ordinarily contain a fairly high concentration or iso-butylene, togethenwithl-butene and '2- butene, normal and'iso-butane aswell as minor amounts of propane andipropylene.

Ordinarily the operation is conducted under pressure, pressures oi frorn'50 to 700 pounds per square inch being preferred: I

With a given concentration of, lso-butene in the original gas, variation in thepressures and 45 temperatures of operation will have some eflect uponthe volatility of the polymer produced; at

3 high temperatures, thepolymers formed tend to have lower boiling points. Moreoventhe'vclatility characteristics ofthepolymers-in the .eflluent gases will establish a minimum temperature of operation, in order to prevent condensation of polymers. These factors are all inter-related, but the operation is in any event so'conducted u d fectiveness so. that it eventually becomes desirlamation and pass out of the In continuous operation, recycling of the gas is not ordinarilydesirable unless the gas consists largely or entirely of iso-butylene. In order to increase the yield of polymers, the best expedient is to increase the time of contact, as for example by passing the gas through a series of reactors containing the acid.

As mentioned hereinabove, the maximum operating temperature will lie in the neighborhood, of

200 C., but in any event should be such asto avoid undesirable oxidational changes. By maintainat temperatures below 200 C. However, due to the fact that these changes cannot be entirely avoided, the acid gradually darkens and loses ef-' able to remove the acid from the system for recseparation of decomposition products therefrom. The darkening of the acid is, howeve'r, much slower than when strong acid is employed, for example, sulfuric acid of -90 per centstrength. I

In a practical embodiment of our invention, a butane cut containing approximately 33.9 per cent'iso-butylene was first saturated with water at about C., under the pressure noted hereinafter, and then introduced into contact with 62.5 per cent sulfuric acid distributed onpumice at an operating temperature of 104 C. and gauge pressure of 30 pounds per square inch. There was obtained a yield of 13.1 per centof polymers, based on the total charge, or20.2 per cent, based on the total unsaturates present in the charge. 76.2 per cent of the resultant polymer boiled below C. Decreasing the strength of the acid gave a lower yield. Increasing the strength of the acid, on the other hand, gave a higher yield but a more volatile product; this is important because the total yield may be increased by simply repeating the operation in a plurality of stages. When this is done, our process makes it possible to obtain a higher total yield of gasoline-like polymers (boiling below 140 C.) than could otherwisebe obtained. 7

At the temperature mentioned, the use of acid over 65 per cent strength gave a considerable evolution of S02, indicating decomposition and side reactions. V Increasing the temperature of operation in general tends to produce a material having a higher volatility ratio, that is to say a material containing a higher proportion of polymers within the gasoline boiling-point range, or, in other words, to increase the relative yield of di-isobutylene as compared with that of tri-iso-butylene.

dinarily be desirable to re-distil the polymers to efi'ect debutanization thereof and also to reduce the polymers to that particular end boiling point After condensation of the polymers, it will'or-' which is suitable'in accordance with use of the polymers as motor fuel, or to separate the dimer from the trimer. and other which may. be formed. i The polymers thus produced, and particularly that fraction boiling tionalvalue'a's motor fuel, having high antiknock value or so-called octane number". Moreover, the di-iso-butylene obtained also represents an advantageous raw material for the preparation of iso-octane, the advantages of which as a motor-fuel are well known.

Wherever sulfur'is present in the original gas in such amount and in such form that the polymers would contain sulfur in a form dimcult to remove by ordinary methods, it is advantageous to subject the gas to a desulfurization treatment in any known-manner before the gas is brought into contact with ,thelpolymerizing agent. ing maximum acid concentration of not more than 65 per cent H2804, however, suchoxidational changes are ordinarily avoided to a large extent It will be apparent tothose skilled in the art that'zwhereas our invention has been described hereinabove in connection with various specific operating details, our invention is'not in its broadcast: aspects limited tosuch operating details, but may be variouslypracticed within the scope of the claims hereinafter made.

What we claim is: p v

1. The process of polymerizing iso-butylene which comprises passing a stream olf gases comprising iso-butylene over a catalyst comprising sulfuric acid of from-about 50 to about 65 per cent strength at atemperature above the dew,

point of the composite polymer in the resultant vaporsiand' gas,'removing the resultant vapors and gas and recovering normally liquidpolymers therefrom. 2.' The process of polymerizing iso-butylene which comprises passinga stream of gases com prising iso-butylene over a catalyst comprising sulfuric acid of from' about 50 to about 65 per cent strength under a pressure of from 50 to Z00 lbs. per square inch and at a temperature lying between about-200 C. and the dew point of the polymer in theresultant vapors and gas, removnormally liquid polymers therefrom.

3. The process of polymerizing iso-butylene which comprises passinga continuous'stream of ing the resultant vapors and gas and recovering butene over a solid absorbent material wetted with sulfuric acid" of from 50 to 65 "per cent strength at atemperature of fromabout 100 C. to about200 C. and under'a pressure of from 50 to 700 pounds per square inch, and separately condensing the resultantpolymers.

4.-The process of polymerizing iso-butylene which comprises continuously passing a stream of butene gas'containing iso butylene over a zone of extended surface, simultaneously introducing sulfuric acid of from 50 to 60 per cent strength vto said zone forconcurrent flow therethro ugh,

maintaining said zone at a temperature of from about 100 to 200 C., removing acid therefromat a strength of from 60 to 65 per cent, adding water thereto to dilute it to a strengthof between 50 and 60 per cent and recycling the diluted acid to said zone for further contact, removing resultant gaseous and vaporous productsfrom said zone and condensing resultant polymers therefrom. DONALD R. S'I'EVENS.

WILLIAM A. GRUSE.

heavier polymers below 140 C. are of excep-' v H c f CERTIFICATE OF CORRECTION. Patent No.:2,;55,117 ,fl H "Novmb ei' 1, 1958 DONALDRQSVTEVVFNS, ET AL." I It i s hereby certified that rrbr appears inth e f pri nted specification of the above 'mimbered patent requiring correcti cn asfcllcm's; Page 2, ccbhd read iso-butylefie; and that thetsaidjLette rc Pgtent should bi'rea'd with this correctionther-ein that same mayfconfcnt to the rec'crd of the m in the Patent Office.

Signed and'sealed this 20th dayfofbecember D. 1958.

Hcriry Van-Arsdalc (seal) i v Acting Coimnissioper of Padaezitez. 

